Muscle Tissue Flashcards
What is myasthenia?
Weakness of the muscle
What is Myoclonus?
A sudden spasm of the muscle
Compare and contrast skeletal, smooth and cardiac muscle.
Skeletal muscle (Striated)- myoglobin present, voluntary control, direct nerve-muscle communication Cardiac muscle(Striated)- myoglobin present, involuntary control, Indirect nerve-muscle communication Smooth muscle (Non striated)- Myoglobin absent, involuntary control, No direct nerve-muscle communication
What is the point of origin in skeletal muscle?
The origin is the attachment site, (typically bone and usually proximal )that doesn’t move during contraction.
What is the point of insertion in skeletal muscle?
The point of insertion is the attachment site (usually bone to tendon, typically distal) that does move during contraction
What do intrinsic muscles connect to?
Other muscles
What do extrinsic muscles connect to?
Bone or cartilage
What allows the tongue to be so mobile?
The plasticity and strength of the connective tissue and the multidirectional orientation of the muscle fibres allow the tongue to be so mobile
What is a muscle fascicle?
A bundle of skeletal muscle fibres surrounded by perimysium (connective tissue carrying nerves an blood vessels)
In a microscope picture what would differentiate a skeletal muscle cell from other cells
Lots of nuclei lined up along the edge of the cell
Which needs more blood to function, thick or thin fibres?
Thick
What is the thin filament called in a myofibril?
Actin
What is the length of a sarcomere?
The distance between Z disc to Z disc
What does titin do?
Acts as a spring in muscle contraction and pulls actin back.
What are slow twitch muscle fibres good for?
Long distance running/ sustained exercise
Compare and contrast slow and fast twitch fibres.
Slow twitch fibres contract slowly, fast twitch contract quickly
slow twitch used for posture, fast twitch used for fast movement
Slow twitch good for endurance, fast twitch good for short bursts of speed and power
Slow twitch don’t fatigue easily, fast twitch fatigue easily
Slow twitch have a slow energy release from aerobic respiration, fast twitch energy is released quickly through anaerobic respiration
Slow twitch have lots of mitochondria, fast twitch have few mitochondria
Slow twitch reddish colour due to myoglobin, fast twitch are whitish due to little myoglobin
Describe the appearance of the microscope picture of cardiac muscle fibre.
Striated, fewer and centrally positioned nuclei, branching (y shaped) and intercalated discs (for electrical and mechanical coupling with adjacent cells)
Name 2 similarities between cardiac and skeletal muscle.
Contraction mechanism is similar
Both are striated muscle
Contrast skeletal muscle with cardiac muscle
In cardiac nuclei are central, in skeletal they’re peripheral
In cardiac sarcomere isn’t as developed
Describe the process of heart rate control.
1) SAN sends out an electrical impulse
2) This causes both atria to contract simultaneously
3) The electrical wave stimulates the AVN. There is a slight delay before the AVN reacts in order to allow the atria to empty completely before the ventricles contract.
4) AVN sends electrical wave along the Bundle of His and the Purkinje fibres.
5) This causes the ventricles to contract simultaneously from the bottom up
Give 4 key features of purkinje fibres?
Cardiomyocytes
Lots of glycogen (a good electrical conductor)
Sparse myofibrils
Extensive gap junctions
Give 3 key features of smooth muscle cells
Capable of being stretched substantially
Contraction is slower, more sustained
Requires less ATP to contract
Forms sheets layers or bundles
What type of stimuli does smooth muscle respond to?
Hormones, nerve signals , drugs, local concs of blood gases
What is hyperplasia?
Multiplication of cells
What is Hypertrophy?
Enlargement of cells
Can adult cardiac cells repair themselves?
No, following damage fibroblasts (specialist connective tissue) invade and lays down scar tissue
Can smooth muscle repair itself?
Yes, smooth muscle cells can undergo mitosis and can form new cells
List the 3 stages of tissue repair
- Acute phase- blood clot forms
- Sub-acute phase- blood clot shrinks, new fibrous tissue formed
- Chronic phase- tissue fibres become organised
Fibre regeneration limited but remodelling continues
DEFINITION OF A STRESS RESPONSE
HGVLYV
Give 3 differences between cardiac and smooth muscle
Smooth muscle don’t contain sarcomeres In cardiac muscle the electrical conduction has specialised cells and routes No troponins (protein integral to muscle contraction) in smooth muscle
Name 4 things that cardiac and smooth muscle have in common
Nuclei are central not peripheral
Only one contractile cell type
Act as a syncytium (wave like function where one muscle cell is linked to another)
Myocytes communicate through gap junctions (cardiomyocytes communicate through intercalated discs)
In a microscope image how could you tell between cardiac and smooth muscle?
Cardiac has intercalated discs (look like vertical lines) and is striated
What do the vesicles contain at the neuromuscular junction?
The neurotransmitter Ach
WHAT IS AN AUTOIMMUNE DISEASE?
An illness that causes the body to produce antibodies that attack normal body tissue. The body views its own tissue as foreign and attacks it.
What is myasthenia gravis? What is a common symptom?
An autoimmune disease where antibodies attack Ach receptors, reducing the number of endplate invagination synaptic transmission and causing intermittent muscle weakness.Patients often suffer from ptosis (drooping eyelid).
What are the protein components of actin?
F-actin fibres
G actin globules
What sits over the actin myosin binding site?
Tropomysosin-troponin complex
What forms the thin filaments of skeletal and cardiac muscle?
Actin, tropomyosin and troponin
What is the role of Calcium ions in muscle contraction?
Calcium ions bind to Tnc of troponin, this causes a conformational (shape) change which moves tropomysosin from the actin binding site which allows the myosin head to attach
In muscle contraction what happens to the Z-lines and sarcomere?
Z-lines become closer together and sarcomere shortens
What is fascia?
A band/ sheet of connective tissue usually collagen that encloses, stabilises or separates muscles and internal organs.
What are the four compartments of the lower leg?
Anterior Compartment
Lateral Compartment
Superficial Posterior Compartment
Deep Posterior Compartment
What is compartment syndrome?
Trauma in one compartment could cause internal bleeding which exerts a pressure on nerves and blood vessels
Define muscle tone
The tension in a muscle at rest.
Define muscle strength
The ability of a muscle to contract and generate force in response to resistance
What 4 things regulate muscle tone?
Motor neurone activity
Muscle elasticity
Use
Gravity
Why do healthy muscles never fully relax?
Retain an amount of stiffness/ tension in order to be ready to react. This can improve with excercise
What is atrophy?
Destruction of cells> regeneration of cells. It means tissue wastes away/ degenerates.
Loss of protein, reduced fibre diameter, loss of muscle power
What is hypertrophy?
Replacement>Destruction. An increase and growth of muscle cells
What’s the mechanism of muscle hypertrophy ?
Over-stretching occurs such that bands A and I can no longer re-engage. New fibrils are made. New sarcomeres are added inbetween existing sarcomeres.
What are the possible causes of muscle atrophy?
Disuse, surgery eg denervation of the muscle, Disease eg muscular dystrophy.
What is duchene muscular dystrophy?
A mutation of the dystrophin gene, inherited X linked recessive pattern ( meaning mum is the carrier of the faulty gene and boys get the disease more).
Absence of dystrophin means excess calcium ions enter the muscle cell, calcium is taken up by mitochondria, water taken up with it, causes lysis of mitochondria, muscle cells burst, CK and myoglobin levels are very high in the blood.
Characterised by muscle degeneration or weakness.
What is rhabdomyolysis?
Striated muscle burst
Rhabdo- Striated Myo-muscle lysis- burst
Give 4 examples of why CK levels may rise
MI Vigorous exercise Rhabdomyolysis Acute kidney injury (myoglobin not being cleared) Muscular dystrophy
What is botulism toxin and what is it used for?
Botulism toxin blocks the neurotransmitter Ach from being released at axon ending ins into the neuromuscular junction, thus causing flaccid paralysis (non-contractile state of paralysis). Clinically used to treat muscle spasms eg cervical dystonia (neck spasm and pain). Cosmetically ‘botox’ can be injected into muscles of wrinkles causing them to relax making them appear smoother
What is the method of organophosphate poisoning?
Acetylcholinesterase is inhibited meaning Ach builds up at the neuromuscular junction
What are the muscular symptoms of patients suffering from cholinergenic toxidrome ( drugs/ chemicals that inactivate cholinesterase’s) ?
S.L.U.D.G.E Salivation Lacrimation Urination Defecation GI cramping Emissions
What are the nicotinic symptoms of patients suffering from cholinergenic toxidrome ( drugs/ chemicals that inactivate cholinesterase’s) ?
M.T.W.T.F Muscle cramps Tachycardia Weakness Twitching Fasciculation’s (small involuntary muscle movements)
What is diplopia?
Double vision
What is ptosis?
Drooping of one or both eyelids
What is dysarthria?
Impaired speech
What is strabismus
Strabismus is more commonly know as ‘cross-eyed’
What is malignant hyperthermia?
It is a type of reaction usually to general anaesthetic in which, the body releases stores of calcium ions which causes muscle contraction, in turn generating excess heat and metabolic acidosis. In general patients are fine when not exposed to general anaesthetic. Common symptoms include muscle rigidity, high fever and tachycardia.
